The 84,700-square-foot AT&T Switching Facility in Walnut Creek, CA, is clad in three varieties of slate from Echeguren Slate, Inc. of San Francisco, CA, which supplied approximately 9,000 square feet of material for the project. According to architect Felix Rodriguez of Garcia/Wagner & Associates of San Francisco, CA, the town administrators of Walnut Creek wanted the facility to fit in with surrounding modern office buildings. The goal, therefore, was to renovate and expand the original building and to create a modern, updated “office building brought forward 40 years,” according to the architect. “The new building had to have increased administrative spaces and equipment areas of which were to be clad in materials of different scale and texture.”

The buildings exterior facade is comprised of 6,600 square feet of 18- x 36-inch panels of Brazilian Green slate, and another 2,000 square feet of the material was used in 20- x 36-inch pieces. Bands of Indian Silver Grey slate - in 10- x 26-inch pieces - and African Silver Blue slate - in 10- x 10-inch pieces - were used to accent the Brazilian Green slate. All of the material was used in 1 ¼-inch-thick pieces.

According to Rodriguez, granite and limestone were both originally considered as finishing materials for the building. “However, administrators felt that the granite and limestone had characteristics that were too similar to the aluminum panels chosen for this project,” he explained. “The City wanted something more aggressive and more contrasting to the gray-colored panels. We couldn't find any limestone that would work, and the granites we looked at were too close in color and of a thick profile. The thicker material also was too costly, and so we started searching for a stone that would work.”


Once the architects chose the slate materials, Hohmann & Barnard, Inc. of Hauppauge, NY - a supplier of attachments for stone products - was consulted to determine the proper thickness of the material. “They ran several tests before they would even get involved with the project,” said the architect. “After they ran all the tests, Echeguren Slate had to make sure that their manufacturer could comply with these standards for the stone.”


Rodriguez said there were a few challenges regarding the project. “The biggest problem was dealing with the seismic factors in California,” he said. ”The entire building surface was out of plumb. We had to shoot every inch of the building to come up with a surface system that was dead flat. The horizontal and vertical planes had to hit an imaginary point in space in order to come up with a flat surface. It was certainly costly and time-consuming.”

Giampoloni Courtney of San Francisco, CA, was in charge of installing the slate for the project. According to Fernando Fernandez, it took a crew of five workers about three months to complete, and the job was straightforward with standard 45-degree clips and angles.

Construction lasted from 2003 to 2006, as the city wanted more and more out of the project. “They kept adding onto the criteria,” said Rodriguez. “Because the city loved the idea behind the project, they required us to remodel the entire city block, which involved new landscaping, lighting and curbing around the building's perimeter.

“The City is very happy with the end result,” he continued. “We often overhear nice comments from people who don't even live in the area.”

AT&T Switching Facility
Walnut Creek, CA

Architect: Garcia/Wagner & Associates, San Francisco, CA

General Contractor: Roebbelen, San Francisco, CA

Stone Installer: Giampolini Courtney, San Francisco, CA

Stone Supplier: Echeguren Slate, Inc., San Francisco, CA

Installation Products: Hohmann & Barnard, Inc., Hauppauge, NY